[] V4641 Sgr : Light curve


The figure shows V-band light curve obtained by KANATA/TRISPEC for the recent 2.5 years. The horizontal axis denotes the orbital phase calculated with a orbital period of 2.81728 days (Orosz et al. 2001). In 2007(red) and 2009(blue), the V magnitudes of V4641 Sgr were almost on the ellipsoidal modulations of its quiescent level. In 2008 (green), we observed some weak brightening events only in 2008 Oct (ATel #1797). We'll continue monitoring of this object for the research of flaring events of the black hole X-ray binaries.


[] GRS 1915+105 : H-band light curve


We have started the 2009-season observation of a black hole X-ray binary GRS 1915+105 in near-infrared bands. The figure shows the H-band light curve from 2008(red dots) to 2009(blue dots). Our recent observations indicates that the object is in the low state in the near-infrared regime.


[] V4641 Sgr: still on the quiescent level


After some cloudy days, we have just restarted our observation of V4641 Sgr. Tonight observation (24 Oct) shows the object apparently stays on its quiescent level.


[] V4641 Sgr: return to quiescence?


We have just finished tonight (21 Oct.) observation of V4641 Sgr. The object is almost on the quiescent ellipsoidal modulation, as can be seen in the above light curve.


[] V4641 Sgr: activity update


The object remains at the slightly active state since the last report. It has kept 0.1-0.2 mag brighter than its quiescent level as can be seen in the above light curve. Tonight (20 Oct.), the object is almost on the quiscent level. The activity may be weakening.